A Wire Bonder is a machine with which semiconductor chips are wired after mounting on a substrate. The Wire Bonder has a capillary that is clamped to the tip of a horn. The capillary serves to secure the wire to a connection point on the semiconductor chip and to a connection point on the substrate as well as to guide the wire between the two connection points. On producing the wire connection between the connection point on the semiconductor chip and the connection point on the substrate, the end of the wire protruding out of the capillary is first melted into a ball. Afterwards, the wire ball is secured to the connection point on the semiconductor chip by means of pressure and ultrasonics. In doing so, ultrasound is applied to the horn from an ultrasonic transducer. This process is called ball bonding. The wire is then pulled through to the required length, formed into a wire loop and bonded to the connection point on the substrate. This last part of the process is called wedge bonding. After securing the wire to the connection point on the substrate, the wire is torn off and the next bonding cycle can begin.
A method and a device for measuring the amplitude of the freely oscillating capillary are known from the U.S. Pat. No. 5,199,630. The measured value is used for calibrating the ultrasonic transducer. The measurement of the oscillation amplitude of the capillary is done by means of a light barrier.
A method and a device for measuring the amplitude of the freely oscillating capillary with which a laser beam is used for the light barrier are known from the Japanese patent 10-209 199.
Experiments have shown that measurement with the known technique does not provide reproducible results when the amplitude of the tip of the freely oscillating capillary is to be measured.